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Structure-preserving properties of three differential schemes for oscillator system

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Applied Mathematics and mechanics(English Edition) 2014年第6期35卷 783-790页

作者：秦丁越邓子辰胡伟鹏 School of mechanics Civil Engineering and Architecture NorthwesternPolytechnical University State Key Laboratory of structural Analysis of Industrial Equipment Dalian University of Technology

A numerical method for the Hamiltonian system is required to preserve some structure-preserving properties. The current structure-preserving method satisfies the requirements that a symplectic method can preserve the symplectic structure of a finite dimension Hamiltonian system, and a multi-symplectic method can preserve the multi-symplectic structure of an infinite dimension Hamiltonian system. In this paper, the structure-preserving properties of three differential schemes for an oscillator system are investigated in detail. Both the theoretical results and the numerical results show that the results obtained by the standard forward Euler scheme lost all the three geometric properties of the oscillator system, i.e., periodicity, boundedness, and total energy, the symplectic scheme can preserve the first two geometric properties of the oscillator system, and the St？rmer-Verlet scheme can preserve the three geometric properties of the oscillator system well. In addition, the relative errors for the Hamiltonian function of the symplectic scheme increase with the increase in the step length, suggesting that the symplectic scheme possesses good structure-preserving properties only if the step length is small enough.

关键词： structure-preserving Hamiltonian system Stormer-Verlet method symplectic

Thermal fluid-structure interaction and coupled thermal-stress analysis in a cable stayed bridge exposed to fire

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Frontiers of structural and Civil Engineering 2018年第4期12卷 609-628页

作者： Nazim Abdul NARIMAN Institute of structural mechanics Faculty of Civil EngineeringBauhaus Universitat WeimarMarienstrasse 1599423WeimarGermany

In this paper, thermal fluid structure-interaction (TFSI) and coupled thermal-stress analysis are utilized to identify the effects of transient and steady-state heat-transfer on the vortex induced vibration and fatigue of a segmental bridge deck due to fire incidents. Numerical simulations of TFSI models of the deck are dedicated to calculate the lift and drag forces in addition to determining the lock-in regions once using fluid-structure interaction (FSI) models and another using TFSI models. Vorticity and thermal convection fields of three fire scenarios are simulated and analyzed. Simiu and Scanlan benchmark is used to validate the TFSI models, where a good agreement was manifested between the two results. Extended finite element method (XFEM) is adopted to create 3D models of the cable stayed bridge to simulate the fatigue of the deck considering three fire scenarios. Choi and Shin benchmark is used to validate the damaged models of the deck in which a good coincide was seen between them. The results revealed that TFSI models and coupled thermal-stress models are significant in detecting earlier vortex induced vibration and lock-in regions in addition to predicting damages and fatigue of the deck due to fire incidents.

关键词： fire scenario transient heat transfer TFSI model coupled thermal-stress XFEM

An analytical poroelastic model for laboratorial mechanical testing of the articular cartilage (AC)

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Applied Mathematics and mechanics(English Edition) 2018年第6期39卷 813-828页

作者： Xiaogang WU Kuijun CHEN Zhaowei WANG Ningning WANG Teng ZHAO Yanan XUE Yanqin WANG Weiyi CHEN shanxi Key Laboratory of Material Strength & structural Impact College of Mechanics Taiyuan University of Technology Taiyuan 030024 China

The articular cartilage （AC） can be seen as a biphasic poroelastic material. The cartilage deformation under compression mainly leads to an interstitial fluid flow in the porous solid phase. In this paper, an analytical poroelastic model for the AC under laboratorial mechanical testing is developed. The solutions of interstitial fluid pressure and velocity are obtained. The results show the following facts. （i） Both the pressure and fluid velocity amplitudes are proportional to the strain loading amplitude. （ii） Both the amplitudes of pore fluid pressure and velocity in the AC depend more on the loading amplitude than on the frequency. Thus, in order to obtain the considerable fluid stimulus for the AC cell responses, the most effective way is to increase the loading amplitude rather than the frequency. （iii） Both the interstitiM fluid pressure and velocity are strongly affected by permeability variations. This model can be used in experimental tests of the parameters of AC or other poroelastic materials, and in research of mechanotransduction and injury mechanism involved interstitial fluid flow.

关键词： articular cartilage (AC) poroelasticity interstitial fluid flow laboratorialmechanical test injury mechanism

Corrections to: structural Optimization of Fiber-Reinforced Material Based on Moving Morphable Components (MMCs)

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Acta Mechanica Solida Sinica 2022年第4期35卷 716-717页

作者： Zhi Sun Ziwen Song Junfu Song Haiyan Li Xu Guo State Key Laboratory of structural Analysis for Industrial Equipment Department of Engineering MechanicsInternational Research Center for Computational MechanicsDalian University of TechnologyDalian116023China

Corrections to:Acta Mechanica Solida Sinica https://***/10.1007/s10338-021-00305-0 During production of the article unfortunately several typesetting mistakes have been *** Eq.(17).

关键词： mistake Morph MMCs

Recent development in structural design and optimization

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Acta Mechanica Sinica 2010年第6期26卷 807-823页

作者： Xu Guo·Geng-Dong Cheng State Key Laboratory of structural Analysis for Industrial Equipment,Department of Engineering mechanics,Dalian University of Technology, Dalian 116023,China State Key Laboratory of structural Analysis for Industrial Equipment Department of Engineering Mechanics Dalian University of Technology Dalian China

With the fast development of computational mechanics and the capacity as well as the speed of modern computers,simulation-based structural optimization has become an indispensable tool in the design process of competitive *** paper presents a brief description of the current status of structural optimization by reviewing some significant progress made in the last *** research topics are also *** entire literatures of the field are not covered due to the limitation of the length of *** scope of this review is limited and closely related to the authors＇ own research interests.

关键词： structural optimization Multi-scale Uncertainty Multi-physics Software

Powell's optimal identification of material constants of thin-walled box girders based on Fibonacci series search method

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Applied Mathematics and mechanics(English Edition) 2011年第1期32卷 97-106页

作者：张剑叶见曙周储伟 Department of mechanics and structural Engineering Nanjing University of Aeronautics and Astronautics Institute of Bridge Engineering Southeast University

A dynamic Bayesian error function of material constants of the structure is developed for thin-walled curve box girders. Combined with the automatic search scheme with an optimal step length for the one-dimensional Fibonacci series, Powell＇s optimization theory is used to perform the stochastic identification of material constants of the thin-walled curve box. Then, the steps in the parameter identification are presented. Powell＇s identification procedure for material constants of the thin-walled curve box is compiled, in which the mechanical analysis of the thin-walled curve box is completed based on the finite curve strip element （FCSE） method. Some classical examples show that Powell＇s identification is numerically stable and convergent, indicating that the present method and the compiled procedure are correct and reliable. During the parameter iterative processes, Powell＇s theory is irrelevant with the calculation of the FCSE partial differentiation, which proves the high computation efficiency of the studied methods. The stochastic performances of the system parameters and responses axe simultaneously considered in the dynamic Bayesian error function. The one-dimensional optimization problem of the optimal step length is solved by adopting the Fibonacci series search method without the need of determining the region, in which the optimized step length lies.

关键词： Powell's theory thin-walled curve box material constant Fibonacci seriessearch method finite curve strip element theory

Control of surface wettability via strain engineering

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Acta Mechanica Sinica 2013年第4期29卷 543-549页

作者： Wei Xiong Jefferson Zhe Liu Zhi-Liang Zhang Quan-Shui Zheng Department of Engineering mechanics and Center for Nano and Micro mechanics Tsinghua University Department of Mechanical and Aerospace Engineering Monash University Department of structural Engineering Norwegian University of Science and Technology (NTNU)

Reversible control of surface wettability has wide applications in lab-on-chip systems, tunable optical lenses, and microfluidic tools. Using a graphene sheet as a sam- ple material and molecular dynamic simulations, we demon- strate that strain engineering can serve as an effective way to control the surface wettability. The contact angles 0 of water droplets on a graphene vary from 72.5° to 106° under biaxial strains ranging from -10% to 10% that are applied on the graphene layer. For an intrinsic hydrophilic surface （at zero strain）, the variation of 0 upon the applied strains is more sensitive, i.e., from 0° to 74.8°. Overall the cosines of the contact angles exhibit a linear relation with respect to the strains. In light of the inherent dependence of the contact an- gle on liquid-solid interfacial energy, we develop an analytic model to show the cos 0 as a linear function of the adsorption energy Eads of a single water molecule over the substrate sur- face. This model agrees with our molecular dynamic results very well. Together with the linear dependence of Eads on bi- axial strains, we can thus understand the effect of strains on the surface wettability. Thanks to the ease of reversibly ap- plying mechanical strains in micro/nano-electromechanical systems, we believe that strain engineering can be a promis- ing means to achieve the reversibly control of surface wetta- bility.

关键词： Wettability ~ Strain engineering ~ Molecular dy-namics simulation

Research on Analytical Method of Fatigue Characteristics of Soft Yoke Mooring System Based on Full-Scale Measurement

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China Ocean Engineering 2017年第2期31卷 230-237页

作者： WU Wen-hua LV Bai-cheng YUE Qian-jin ZHANG Yan-tao LIN Yang Department of Engineering mechanics State key Laboratory of Structural Analysis of Industrial EquipmentDalian University Tianjin Branch CNOOC

By focusing on the vulnerability of the structure of marine equipments, together with considering the randomness of meta-ocean load in statistics, a kind of analytical method of fatigue characteristics of marine structure based on full- scale and actual measurement of prototype is proposed. On the basis of short-term field measurement results of structural response, research is carried out on the fatigue analysis of hinge joints at the upper part of the Soft Yoke single point Mooring System （SYMS） by simultaneously monitoring the environmental load and considering the design criteria of offshore structure. Through analysis of finite element modeling, the time-histories of typical stress response are obtained, and then the assessment of fatigue damage at key hinge joints is conducted. The simulation results indicate that the proposed method can accurately analyze the fatigue damage of offshore engineering structure caused by the effect of wave load. The present analytical method of fatigue characteristics can be extended on other offshore engineering structures subjected to meta-ocean load.

关键词： fatigue characteristics full scale measurement finite element method SYMS

New analytic solutions to 2D transient heat conduction problems with/without heat sources in the symplectic space

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Applied Mathematics and mechanics(English Edition) 2022年第8期43卷 1233-1248页

作者： Dian XU Xinran ZHENG Dongqi AN Chao ZHOU Xiuwen HUANG Rui LI State Key Laboratory of structural Analysis for Industrial Equipment Department of Engineering Mechanicsand International Research Center for Computational MechanicsDalian University of TechnologyDalianLiaoning Province116024China

The two-dimensional(2D)transient heat conduction problems with/without heat sources in a rectangular domain under different combinations of temperature and heat flux boundary conditions are studied by a novel symplectic superposition method(SSM).The solution process is within the Hamiltonian system framework such that the mathematical procedures in the symplectic space can be implemented,which provides an exceptional direct rigorous derivation without any assumptions or predetermination of the solution forms compared with the conventional inverse/semi-inverse *** distinctive advantage of the SSM offers an access to new analytic heat conduction *** results obtained by the SSM agree well with those obtained from the finite element method(FEM),which confirms the accuracy of the SSM.

关键词： heat conduction heat source symplectic superposition method(SSM)